Published: October 29, 2013

WASHINGTON — President Obama finds himself under fire on two disparate fronts these days, both for the botched rollout of his signature health care program and for the secret spying on allied heads of state. In both instances, his explanation roughly boils down to this: I didn’t know.

As a practical matter, no president can be aware of everything going on in the sprawling government he theoretically manages. But as a matter of politics, Mr. Obama’s plea of ignorance may do less to deflect blame than to prompt new questions about just how much in charge he really is.

In recent days, the president’s health and human services secretary said that despite internal concerns and a failed test run Mr. Obama was not told about serious problems with the new program’s website until it was rolled out this month. Other officials said the president was not aware that the National Security Agency was tapping the phone of Chancellor Angela Merkel of Germany and other friendly leaders until this summer, although intelligence officials said Tuesday that others in the White House had known.

Opposition lawmakers and pundits have seized on the White House explanations to accuse Mr. Obama of being a “bystander president,” as the Republican National Committee put it. Even some Democrats are scratching their heads at the seeming detachment from significant matters. MSNBC’s “Morning Joe” ran a montage of clips showing Mr. Obama or his aides disclaiming presidential knowledge of various issues as well as a graphic titled “Implausible Deniability.”

“It seems to me there’s a pattern here — with any bad news coming out of the administration, the excuse is the president just didn’t know about it,” said Representative Adam Kinzinger, Republican of Illinois.

“There’s a point at which the I-didn’t-know excuse really violates the idea of the buck stops here,” he added. “We want to have a feeling that the president ultimately takes responsibility. The American people want to know they have a president who’s in control and in charge.”

Democrats were less likely to blame the president but suggested that he was ill served if other officials did not keep him fully abreast. “If people really knew there were to be problems, I was a little surprised that people at the highest levels weren’t aware,” Patrick Griffin, who was a top White House official under President Bill Clinton, said of the health care program.

As for the N.S.A. surveillance, Senator Dianne Feinstein of California, the Democrat who leads the Senate Intelligence Committee, put it sharply in a statement she released earlier this week. “It is my understanding that President Obama was not aware Chancellor Merkel’s communications were being collected since 2002,” she said. “That is a big problem.”

Aides dismissed suggestions that Mr. Obama did not pay enough attention in either of these areas. On the spying program, they said the president was deeply immersed in details of the nation’s surveillance practices but was focused on those areas that constituted the major threats to the United States. He had no reason to suspect that Ms. Merkel or other leaders of close allies were being tapped, nor did he think to grill anyone about it because that was not a high priority, they said.

On health care, aides said that Mr. Obama had been fixated on details of the law’s carrying out and that advisers did not withhold information but were likewise surprised by the scope of the problems.

“From the moment the health care bill was signed into law the president was very focused on making sure it was implemented correctly,” said Dan Pfeiffer, a senior White House adviser. “In just about every meeting, he pushed the team on whether the website was going to work. Unfortunately, it did not, and he’s very frustrated.”

Mr. Pfeiffer insisted that the president wants to hear what he needs to hear and would not accept advisers’ keeping negative information from him. “He’ll know if you don’t tell him the bad news he needs to hear, and that’s the quickest way to be on the outside looking in,” Mr. Pfeiffer said.

The challenge for any president is keeping on top of a vast array of issues, any one of which could blow up at any given time. Harry S. Truman spoke for many of his successors when he said that “the pressures and complexities of the presidency have grown to a state where they are almost too much for one man to endure.” And that was decades before metadata technology came along.